WD-40 is made for drying electrical parts. WD = water displacement. It came to fame after a hurricane in Texas and was widely used on flooded electric panels. While there is a little oil in the mix, it really isn't for lubrication. There are many better products that do a better job of lubing small parts. Too much oil poured into a diesel can cause hydraulic lock or at worse cause extreme compression/ignition pressures, like too much ether. Starting on too much ether over a short time will make pistons like the ones shown. At best cracked rings.

WD-40 isn't used as an electrical "water displacement" product. In fact, it's electrically conductive, so not what you'd want to use. This said, many do use it because it's cheap, but it has to be cleaned off of contacts and devices before being energized again. It's best to use a product actually designed to clean electrical devices and one that doesn't leave a conductive residue.

‘‘ WD-40 is safe to use on electrical equipment, but we always recommend checking with the manufacturer first. WD-40 is non-conductive and will not harm components. It is especially good at displacing moisture from electrical equipment. ’’

Post #11 there is posted by forum member ‘‘Original WD-40’’, I don't know if that's a WD-40 company poster . . ?

It says in post #1 that WD-40 became a non-conductive coating like an insulator between the fuses and their contact clips, which prevented the whole machine from working, till it was sanded off (it looks like only sandpaper was at hand at the time).

If so, then I'll guess the same can happen to the contacts in switches, light bulbs, etc., like is warned for there.

My bad, as I assumed it was electrically conductive from previous experience with it. I have used it to clean and displace water, but always used a contact cleaner afterward to remove the film. I have switches and devices stop working after an application of WD-40 and have since always used a real electrical contact cleaner to remove residual films.

My experience from reading these forums is that makes far less than 1 ‰, so no reason for worries I think, and your main message that it can cause problems turned out to be right, so I'll guess that's why WD-40 also offers an Electrical Contact Cleaner, which corresponds to your advice to use such a product.

This will sound strange. I’ve removed the air cleaner on a seized V8 gas engine poured a can of coke cola through the carb. Went back an hour later the engine turn about 60 degrees pour another can of coke in the carb. Came back to it an hour later and it bared over completely. Hooked up new gas and battery and drove it away

I hope you've also changed the engine oil after the cola released the pistons and rings from the cylinders, since the cola might have entered the engine oil, and cola doesn't seem to be a good substitute for oil in a running engine . . .

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